Specifically in this collaborative study our overall objectives will be: 1. To have a relatively large number of subjects; 2. To use standardized criteria for diagnosis; 3. To use comparable quantitative measures of several potentially confounding behavioral state variables; 4. To assess by standardized methods the baseline functioning of amine, neuroendocrine, and electrolyte systems in each individual patient and in comparison subjects; 5. To examine the possiblility that baseline or pretreatment biological measures are associated with response or non- response to different tricyclic anti-depressants. 6. To examine interrelationships between biological systems now considered of significance in the development or peristence of affective illness. Particular emphasis will be given to the distinct possibility that the genesis of the affective disorders resides in interactions between the activity of systems and not in a deficit in a single system. For example, relationships between the serotonergic and noradrenergic systems and how they may respond to neuroendocrine or electrolyte changes.